1. Field of the Invention
The present invention relates to a numerical controller for controlling a machine tool, and more particularly to a numerical controller for drivingly controlling respective axes in accordance with data stored in the form of a table.
2. Description of Related Art
Conventionally known is a numerical controller in which motion amounts and positions of individual axes are previously stored in a table format, and the axes are drivingly controlled based on the data stored in the table, not on block commands from an NC program. Thus, according to this arrangement, a tool can be freely operated without being restricted by the conventional block commands, so that the machining time is shortened and the machining accuracy is enhanced.
According to a well-known invention (see JP 59-177604A), a position of a movable axis for each time or rotation angle, for example, is previously stored as numerical control data, the time or rotation angle is monitored, and the numerical control data corresponding to the movable axis is outputted every time the stored time or rotation angle is attained.
According to another known invention (JP 2003-303005A), a data table is previously provided for storing command positions of X- and Z-axes for a reference position, and the reference position is obtained by multiplying a value in a counter for counting reference pulses by an override value. Based on this reference position, the X- and Z-axis command positions stored in the data table are outputted to perform synchronous control of the X- and Z-axes, whereby an override can be entered even in drive control based on the data stored in the data table. Further, the command positions can be connected based on linear, quadratic, or cubic functions, and a command can be issued for an auxiliary function.
In operation (hereinafter referred to as path table operation) such that the axes are driven in response to commands based on the table format data described in JP 2003-303005A, the auxiliary function commanded by the table format data can be outputted together with commands for the axis positions. Unlike auxiliary functions based on conventional NC sentences, the auxiliary function can be outputted at any desired time or spindle position, so that the output timing can be optimally adjusted to shorten the machining time.
Since the actual auxiliary function is subject to an operation delay, however, its operation is correspondingly delayed behind its output. In order to adjust the output timing optimally, therefore, the auxiliary function must be outputted earlier in consideration of the operation delay. If the time or spindle speed is overridden in the path table operation, moreover, the timing for actual operation varies depending on the set override value or actual spindle speed despite the hastened output. Thus, data must be prepared taking account of the actual override value, so that the data adjustment takes a lot of time, and the machining cycle is wasteful.